It's sold at Lowes. It's a 1/4" thick, blue insulation board.[&:] It comes in a bundle about 3 1/2' square and folded back and forth making like a cube. It cost about $30./$35. and there's enough to make at least a dozen or more planes. There are plenty of free plans for using the stuff right here somewhere.[sm=spinnyeyes.gif] D'oh! [sm=lol.gif]GWR